build.rs.txt

#[macro_use]
extern crate serde_json;
#[macro_use]
extern crate json_config;

use json_config::ConfigurationBuilder;
use json_config::ConfigurationSource;
use json_config::ConfigurationDefinitionParams;

pub fn main(){
    let base_config_str = r#"
    {
        "appName": "json_config Demo",
        "appVersion": 1.5,
        "database": {
            "host": "dev.database.com",
            "port": 3000
        }
    }"#;

    let mut builder = config!(vec![        
        from_str!(base_config_str),
        from_file!("config/translations.json"),
        from_file!("config/keystore.json"),

        bundle!("QA", vec![
            from_json!({
                "database": {
                    "host": "qa.database.com",
                    "port": 3001
                }
            }),
            from_file!("config/keystore_qa.json")  
        ]),

        bundle!("PROD",vec![
            from_json!({
                "database": {
                    "host": "prod.database.com",
                    "port": 3002
                }
            }),
            from_file!("config/keystore_prod.json") 
        ])
    ]);
       
    //execute cargo build after setting the environment variable JSON_CONFIG_ENV
    //i.e. set JSON_CONFIG_ENV=QA on Windows 
    //i.e. export JSON_CONFIG_ENV=QA on Linux/MacOS
    builder.merge_bundle(env!("JSON_CONFIG_ENV"));
    builder.to_compiled("json_config.json");
}